For the third and final time, Hillary Clinton and Donald Trump will debate Wednesday night. It may be the Republican's last chance to shake up a race that some polls have Hillary Clinton handily winning. Josh Robin has a preview.

They shook hands at the start the first time, just said hi the second — who knows what Donald Trump and Hillary Clinton will do in the third, other than try for a final time to convince the nation the other is the pits.

"I'm sorry I have to keep saying this, but he lives in an alternate reality," Hillary said.

"There has never been so many lies, so much deception," Trump said.

Moderator Chris Wallace of Fox News plans questions on debt and entitlements, immigration, economy, Supreme Court, foreign hot spots and fitness to be President. Trump likely needs a really big night. National polls show him losing. Post-debate polls show voters are skeptical about him at best.

"In both cases, only about 35 percent of voters said the debate made them feel Trump was prepared," said Tom Jensen with Public Policy Polling. "Only about 35 percent said the debate made them think Trump had the temperament to be president. So he's been failing on those tests, and he really needs to pass on the last debate if he's gonna have any hope of a comeback."

"My temperament has always been just about my greatest strength," Trump said at the first debate last month.

Rallying in Colorado Tuesday, Trump mocked Clinton's debate prep.

"She's been doing this for 30 years, now she has to do debate prep for five days," Trump said. "You know what the debate prep is? It's resting."

As she arrives in Las Vegas Clinton is relying on surrogates.

"There's been quite enough acid poured down the throat of the American people in the last 15 months, to last us for the next 15 years," said Bill Clinton.

Then there is the audience. Those attending are routinely instructed not to disrupt what happens on stage. But last time, Trump apparently tried to rattle Clinton by bringing in special guests.

They were women accusing Bill Clinton of sexual misconduct. It is unclear who Trump is taking this time. Clinton invited Dallas businessman Mark Cuban, who has been needling Trump.

It will be political theater, and perhaps some policy thrown in.